I did see that comment from XVortex, and it raised the question in my mind of what RMerlin is doing with IPv6, since he's recently reworked it and it is working well on my RT-AC68P. I'm waiting to see RMerlin himself comment on what he's doing with IPv6. None of RMerlin's comments that I've seen about his next release have mentioned IPv6. Which, of course, doesn't exclude it, but it isn't the first thing on his mind *smile*.
Even more interesting is that the Quantenna SoC has its own Gigabit Ethernet port. So Ethernet traffic to port 1 (if my interpretation of the board photo supplied by RMerlin and is correct), has to travel through RGMII ports to get to the WAN or ports 2-4.
Starting to wonder if the 32 KB nvram isn't actually more a bug than a stupid design decision...
IPv6 is also working on dd-wrt that I'm currently using on my R7000, although it doesn't correctly filter ICMPv6 packets. RMerlin's firmware on the RT-AC68P does do that filtering properly, and tomato ARM does the filtering correctly as well, the rest don't *smile*. Netgear and Linksys stock don't filter ICMPv6 packets correctly, same as dd-wrt.
RMerlin confirmed that all 5 GHz band processing, including Ethernet / Wi-Fi packet conversion is handled by the Quantenna section. He also pointed me to this recent , extolling the AC87's superior design. The detailed block diagram from that post provided some interesting information.